Not Applicable.
1. Field of the Invention
This invention relates to automotive service wheel balancers with the capability of measuring tire uniformity and in particular to an improved system to check centering of wheels mounted on wheel balancers.
2. Description of the Prior Art
Wheel balancers determine unbalance in vehicle wheel/tire assemblies by an analysis of the mechanical vibrations caused by rotating the wheel/tire assembly. The mechanical vibrations are measured as motions, forces, or pressures by means of transducers, which convert the mechanical vibrations to electrical signals. Wheel/tire assembly unbalance may result from unbalance in the wheel, unbalance in the tire, or both.
Even when a wheel/tire assembly is balanced, non-uniformity in the construction of the tire as well as runout in the wheel rim can cause significant vibration forces as the wheel rolls under vehicle load. Most tire manufacturers inspect their tires on tire uniformity machines and grind rubber off the tires as required to improve rolling characteristics of the tires. Even after this procedure, tires will often produce vibration forces (not related to imbalance) of 20 pounds as they roll on a smooth road.
SAE recommended practice J332 describes testing machines for measuring the uniformity of passenger car and light truck tires. Machines conforming to J332 are used by tire manufacturers, but they are large and expensive and not affordable for automotive service use.
Only a few models of machines capable of measuring tire uniformity have been offered to the automotive service industry. One such machine was the Tire Matcher System 6000 (trademark) which was manufactured by Ride Control Systems Inc. in the 1980s. This machine measured the radial force variation and then buffed the tire in selected areas to bring the radial force variation within acceptable limits. This machine did not match the wheel to the tire and did not balance the wheel/tire assembly. The Dynabal Corporation manufactured a wheel balancer in the early 1990s which had the capability to measure the radial force variation of a wheel/tire assembly and the wheel rim runout. This machine displayed the angular location to mount the tire onto the wheel to minimize the wheel/tire assembly radial force variation. The GSP9700 manufactured by Hunter Engineering is another balancer which measures wheel/tire assembly radial force variation and rim runouts. This balancer also will display the angular location to mount the tire onto the rim to minimize the wheel/tire assembly radial force variation. The above machines do not show the user how to take a set of two or more wheel/tires assemblies and cross match the tires and wheels to come up with the best pairing of wheels to tires.
Prior art balancers also have more subtle deficiencies that arise in connection with compensating for run-out and in tire matching. For example, wheel rim runout is frequently measured from the xe2x80x9coutsidexe2x80x9d of the rim (i.e., that portion of the wheel rim that is exposed to view once the tire is mounted thereon. If the wheel rim runout measured on the xe2x80x9coutsidexe2x80x9d portion of the rim does not correspond to the runout of the bead seat surface itself (which is on the xe2x80x9cinsidexe2x80x9d), errors in the tire matching/compensation process can be introduced.
Even if the actual bead seat is used to measure runout, errors can still result. For example, if the bead seat method is used to obtain runout, the rim must be removed from the balancer for mounting the tire and then remounted to the balancer to measure wheel/tire assembly force variations. Any centering difference with respect to the spindle of the balancer will result in errors in the determination of the rim runout, the assembly force variation, and the tire force variation computation. This xe2x80x9ccentering errorxe2x80x9d can become even more significant with larger wheel/tire assemblies.
Similarly, with conventional equipment, after mounting the tire on the rim the rim must be mounted at exactly the same angular position relative to the spindle as it was mounted in the rim runout measurement step. Otherwise the angle of the recalled rim contribution will be incorrect and so will the resulting tire computation.
Some of the deficiencies of prior art balancers are addressed by co-assigned U.S. Pat. No. 6,336,364, which is incorporated herein by reference.
Among the various advantages and features of the present invention is a wheel balancer for use in tire matching which has improved performance.
Another advantage is the provision of such a wheel balancer that readily detects centering errors resulting from the improper remounting of a wheel or a wheel/tire assembly on the balancer.
A third advantage is the provision of such a wheel balancer that prevents errors resulting from the rotational angle at which a rim is remounted on the balancer.
A fourth advantage is the provision of such a wheel balancer with improved vibration reduction in the balanced wheel/tire assembly.
A fifth advantage is the provision of such a wheel balancer with improved tire rejection rates.
Other advantages and features will be in part apparent and in part pointed out hereinafter.
Briefly, in a first aspect of the present invention a method of matching a tire to a wheel includes the steps of mounting the bare wheel on a spindle of a wheel balancer, providing to the balancer a signal indicative of the relative rotational position of the wheel with respect to the spindle, determining the run-out of the wheel rim, mounting a wheel/tire assembly on the balancer spindle, the wheel/tire assembly consisting of the tire mounted on the wheel, determining force variation of the wheel/tire assembly, visually indicating a relative rotational mounting position of the tire with respect to the wheel to minimize the wheel/tire assembly force variation, repeating the previous steps with at least one additional wheel and wheel/tire assembly, and matching the tires with the wheels so as to minimize force variation for the wheel/tire assemblies as a group.
In a second aspect of the present invention, a method of matching a tire to a wheel includes the steps of mounting the bare wheel on a spindle of a wheel balancer, providing to the balancer a signal indicative of the relative rotational position of the wheel with respect to the spindle, determining the run-out of the wheel, mounting a wheel/tire assembly on the balancer spindle, the wheel/tire assembly consisting of the tire mounted on the wheel, providing to the balancer a signal indicative of the relative rotational position of the wheel/tire assembly with respect to the spindle, determining force variation of the wheel/tire assembly, and visually indicating a relative rotational mounting position of the tire with respect to the wheel to minimize the wheel/tire assembly force variation.
In a third aspect of the present invention, a method of matching a tire to a wheel by adjusting the rotational positions of the tire with respect to the wheel to compensate for wheel rim run-out and force variations includes the steps of measuring rim run-out from the exterior of the wheel to obtain a first rim run-out measurement, measuring rim run-out from the bead seat to obtain a second rim run-out measurement, and compensating the force variation measurement for differences in the first and second rim run-out measurements.
In a fourth aspect of the present invention, a method of balancing a wheel/tire assembly consisting of a wheel and a tire includes the steps of mounting the wheel on a spindle of a balancer, measuring rim run-out from the exterior of the wheel rim without a tire mounted thereon to obtain a first exterior rim run-out measurement, mounting a tire on the wheel rim to form a wheel/tire assembly, mounting the wheel/tire assembly on the spindle of the balancer, measuring rim run-out from the exterior of the wheel with a tire mounted thereon to obtain a second exterior rim run-out measurement, and remounting the wheel/tire assembly on the balancer if the rim run-out measurements differ by an amount indicating that the wheel was not centered properly on the spindle during one of the rim run-out measurements.
In a fifth aspect of the present invention, a method of matching tires to wheels by adjusting the rotational positions of the tires with respect to the wheels to compensate for wheel run-out and wheel/tire assembly force variations includes the steps of sequentially mounting a plurality of wheel/tire assemblies on a spindle of a balancer, measuring the rim run-out for each assembly and the force variations for each assembly, marking each tire of each assembly to identify both the individual tire and the rotational position representing the first harmonic of the tire force variation at which each tire is mounted with respect to its wheel, removing each tire from its wheel, sequentially mounting the wheels with tires removed on the spindle of the balancer, measuring the rim run-out for each rim, and visually indicating to a user a preferred matching between the tires and the wheels to minimize assembly vibration.
In a sixth aspect of the present invention, a method of matching tires to wheels includes the steps of mounting a bare wheel to a spindle of a wheel balancer, measuring run-out of the wheel rim, visually identifying the wheel whose run-out has been measured, mounting a tire on the wheel to form a wheel/tire assembly, mounting the wheel/tire assembly to the spindle, measuring the force variation of the wheel/tire assembly as it is spun on the balancer, compensating the measured force variation for the force variation due to wheel run-out to determine force variation of the tire, visually indicating to the user proposed matching locations on the tire and the wheel, manually marking the proposed matching locations on the tire and the wheel, repeating the previous steps for any additional wheels and tires as desired to create a set of tires and wheels with proposed matching locations marked thereon, automatically determining the best combinations between the tires and wheels that have been marked to reduce vibration, and mounting the tires on the wheels in the automatically determined best combinations.
In a seventh aspect of the present invention, an apparatus for matching tires to wheels includes a balancer having a spindle on which wheels and wheel/tire assemblies may be mounted for determining force variations and wheel rim runout. The balancer further includes a computer programmed to predict force variation for a given tire mounted on a plurality of wheels, said wheels having known run-out characteristics.
In an eighth aspect of the present invention, an apparatus for matching tires to wheels includes a balancer having a spindle on which wheels and wheel/tire assemblies may be mounted for determining force variations and wheel rim runout, and a computer programmed to predict force variation for a given wheel having mounted thereon a plurality of tires, said tires having known force variation characteristics.
In a ninth aspect of the present invention, a method of matching tires to wheels includes the steps of mounting a bare wheel to a spindle of a wheel balancer, measuring run-out of the wheel rim, visually identifying the wheel whose run-out has been measured, mounting a tire on the wheel to form a wheel/tire assembly, mounting the wheel/tire assembly to the spindle, measuring the force variation of the wheel/tire assembly as it is spun on the balancer, compensating the measured force variation for the force variation due to wheel rim run-out to determine force variation of the tire, visually indicating to the user proposed matching locations on the tire and the wheel, manually marking the proposed matching locations on the tire and the rim, repeating the previous steps for any additional wheels and tires as desired to create a set of tires and wheels with proposed matching locations marked thereon, automatically determining the best combinations between the tires and wheels that have been marked to reduce vibration, and repeating the prior steps until at least four sets of tires and wheels are matched, further including a visual indication to the user of the positions on the vehicle at which each of said four sets of tires and wheels should be mounted, and a visual indication to the user of the rotational position at which each tire should be mounted with respect to its matched wheel.